Make HDR code build on systems where patched Qt is not available
You need to add -DHAVE_HDR to enable HDR-related code. But
you will need a patched Qt for that.
The patch also makes the code behave correctly on Linux
systems.
PS:
The patch also makes it possible to select OpenGL ES renderer
on Linux. The renderer is selected fine, but doesn't work for
some reason. I guess some texture format is set incorrectly.